JP5476390B2 - Electrosurgical device having a temperature measuring device - Google Patents

Description

The invention relates to an electrosurgical device according to the preamble of claim 1 and a method for determining temperature and / or temperature changes in a neutral electrode according to claim 15 .

  In high frequency surgery, electrical energy is supplied to the tissue to be treated. In this respect, generally, a monopolar application and a bipolar application of a high frequency current (HF current) are distinguished.

  In the monopolar application, normally, only one active electrode is provided, and a high-frequency AC voltage is applied thereto. The active electrode is positioned, for example, on an electrosurgical instrument for cutting and / or coagulating tissue. In order to form a current circuit through the tissue located between the active and neutral electrodes, it is also necessary to apply a neutral electrode to the patient's body. The type of active electrode depends on the application given to it. The surface of the active electrode that conducts the alternating current into the tissue is relatively small, thus causing a high current density and inevitably a high level of heat generation in the immediate vicinity of the active electrode.

  The current density decreases rapidly as the distance from the active electrode increases, provided that no high current density occurs in other body parts as a result of the substantial difference in tissue conductivity. The AC voltage applied to the active electrode is guided outside through the neutral electrode. It should be noted that the neutral electrode is applied over a large area of the patient's body and thus exhibits a low contact resistance to high frequency alternating current.

  In bipolar application, two active electrodes are provided and the tissue to be treated is placed between them. The current flow is directed through the tissue lying between the two active electrodes, so that the tissue is heated when a high frequency current is applied. Most of the current flows between these two active electrodes.

  There may be situations where the neutral electrode is not properly applied to the patient or the electrode is partially detached during the procedure. In such a case, the current flow is limited to the still contacted part of the neutral electrode, which can thus cause a significantly higher impedance in said part and, in general, a higher current density in the adjacent tissue. is there. As shown in the reference prior art document described later, a monitoring system capable of evaluating the sticking quality of a neutral electrode is known.

  For example, DE 10 2004 025 613 B4 discloses a method for determining the contact impedance between two partial electrodes or between electrode sections of a divided neutral electrode in high frequency surgery. ing. In this case, the contact impedance is determined by the oscillation circuit between the two electrode sections. For neutral electrodes with a large contact area, it can be assumed that the contact impedance between the individual sections is significantly lower.

  In recent years, treatment methods have been developed in which a relatively large high-frequency current is applied for a relatively long time. This method increases the risk of burning the tissue at the neutral electrode. Therefore, even when the neutral electrode is correctly applied, the tissue may still be damaged depending on the treatment method or the course of treatment. Theoretically, it is conceivable to further increase the contact area of the neutral electrode, but this is often not suitable for practical use.

  It is therefore necessary to monitor the temperature at the neutral electrode. US 2006/0079872 A1 discloses a device for this purpose. According to this document, a resistor is coupled into the therapeutic current, in which case the heating of the resistor can be monitored with a thermal sensor. The resistor should be selected to simulate an almost actual impedance state between the neutral electrode and the active electrode. However, proper selection of resistors is extremely difficult because impedance values vary from application to application depending on the method used, instrument, instrument alignment and neutral electrode, tissue being treated, etc.

  In addition, an approach is considered in which a commercially available temperature sensor is considered to be mounted directly on the electrode. However, it is very complicated to equip the electrodes with the measuring device. Furthermore, local heating often occurs that may not be detected by the sensor.

  In principle, the impedance between the two divided halves of the neutral electrode is measured as described above. Since resistance is proportional to the contact area, this provides a guide value for the contact area. In addition, the current is measured by the neutral electrode and is used with the contact resistance to estimate the theoretical power loss experienced at the electrode. This power loss can be compared to an empirically determined limit value to conclude with respect to the temperature at the neutral electrode. However, these approaches are prone to errors and cannot provide reliable protection against injury to the patient. Also, different types of organizations are not considered in this approach.

German Patent No. 10 2004 025 613 B4 Specification US Patent Application Publication No. 2006/0079872 A1

  In view of this prior art, in particular US 2006/0079872 A1, it is an object of the present invention to provide an electrosurgical device having an improved temperature measuring device. Furthermore, a corresponding method for determining the temperature and / or temperature change at the neutral electrode is also provided. Specifically, the present method and device enable reliable and efficient evaluation of temperature conditions at neutral electrodes.

  This object is achieved according to the invention by an electrosurgical device according to claim 1.

Specifically, this purpose is as follows:
A high-frequency generator for generating a high-frequency current that can be guided into the living tissue (3) via the instrument (20) and a neutral electrode (10) having a contact agent layer (13);
A temperature measuring device for determining the temperature and / or temperature change at the neutral electrode;
An electrosurgical device comprising:
This purpose is
This is solved in that the temperature measuring device for determining temperature and / or temperature change comprises an impedance measuring device configured to detect the impedance of the contact agent layer.

  Therefore, the central concept of the present invention is to estimate the temperature of the neutral electrode or its temperature change based on the measurement of impedance. In line with this purpose, the neutral electrode according to the invention has a contact layer with a temperature-specific impedance. The electrical resistance of the contact agent layer varies depending on the dominant temperature. Temperature-specific impedance in the sense of the present invention should be understood as meaning a change in impedance depending on the temperature within the relevant temperature range. In the case of electrosurgery, the relevant temperature range lies between 10 ° C. and 100 ° C., but possibly between 20 ° C. and 70 ° C., in particular between 20 ° C. and 60 ° C., may be sufficient.

  Preferably, the contact agent layer has material properties such that the impedance decreases with increasing temperature, particularly within the relevant range. Given local heating of the neutral electrode, the impedance measurement is reduced. Therefore, the impedance measuring device can always detect the lowest impedance, that is, the hottest portion of the contact agent layer.

  The impedance measurement device can comprise a measurement current generator, which is configured to provide a measurement current at the first electrode section and the second electrode section. Accordingly, the neutral electrode is preferably subdivided into at least one first electrode section and at least one second electrode section. Impedance measurements can be effectively ensured between these two electrode sections. It is also conceivable to measure a plurality of impedances between a plurality of electrode sections. In this way, improved detailed resolution of the temperature state at the neutral electrode is achieved. Therefore, the neutral electrode is useful not only for the application of a high-frequency current but also for determining the impedance or impedance state inside or in the contact agent layer.

  The measurement current generator can be configured to supply a measurement current with an alternating voltage, in particular an alternating current having a frequency of 300 kHz or less, specifically 150 kHz or less, more specifically 100 kHz or less. It may be configured to supply a measurement current with voltage. With such a frequency lower than that used for high frequency current treatment, an effective measurement of impedance can be performed. It is also conceivable to separate the measurement current and the high-frequency treatment current from each other by means of a filter and evaluate them separately.

  The electrode sections can be arranged on the contact agent layer and electrically insulated from each other. In order to generate different potentials in the individual electrode sections, it is necessary to configure these electrode sections to be electrically isolated from one another.

  The high frequency generator may be configured to provide a high frequency current with an alternating voltage exhibiting a frequency of 300 kHz or higher, more specifically 1000 kHz or higher. Such frequencies are standard in high frequency surgery and are suitable for performing effective coagulation and disruption of tissue. These frequencies are significantly different from the frequencies used for the measurement current. A frequency filter can be used to separate the measurement voltage and the high frequency voltage.

  The contact agent layer has an electrical impedance having a high temperature dependency, in particular an electrical impedance having a (relative) impedance change of 1% or more per degree Celsius, specifically 2% or more Celsius. It is possible. The higher the temperature dependency of the contact agent layer used, the more easily the temperature change can be detected by the impedance change. Preferably, the relative impedance change within the relevant temperature range is greater than 1% per degree Celsius.

  The contact agent layer can comprise a hydrogel or can consist of a hydrogel. Preferably, the contact agent layer is made from a hydrogel. Upon application of high frequency current, the hydrogel is used to reduce the contact resistance between the electrode and the skin. The impedance of a hydrogel has a strong dependence on its temperature. Thus, the hydrogel is optimal for performing temperature detection according to the present invention. In this case, the hydrogel has a dual function. First, the hydrogel serves for better application of high frequency current and / or mechanical clamping of the neutral electrode to the patient, and second, it is also part of the temperature sensor.

  The temperature measurement device can comprise an impedance integration device, which is configured to integrate the impedance change over a predetermined period of time to perform thermal equilibrium estimation. Long-term observation (by integration over time) of impedance changes across all heating and cooling phases during the course of treatment intervention provides a realistic estimate of thermal equilibrium at the neutral electrode and thus a reliable assessment of the thermal situation.

  The predetermined period of time can cover a plurality of activation and deactivation stages of the high frequency generator. Therefore, in the temperature evaluation, it is possible to consider both heating during the activation stage in which the high-frequency current is applied and cooling during the non-activation stage in which the high-frequency current is not applied.

  The electrosurgical device may comprise a recognition device for determining parameters, in particular at least one electrode area and / or temperature coefficient parameter of the neutral electrode. The impedance value measured at the neutral electrode depends on several factors. Such elements include the area of the neutral electrode, specifically the area of the electrode sections, their position relative to each other, tissue resistance, etc. Parameters relating to the calculation of the temperature of a particular device and in particular a particular neutral electrode can be stored. The recognition device can determine or read these parameters, and can process these parameters in an associated model or calculation.

  The recognition device may comprise a database having a plurality of parameters and a plurality of neutral electrode types, in which case the recognition device detects a connection of a specific neutral electrode type and the parameters are appropriately stored in the database. Configured to read from. Thus, the determination of the neutral electrode to be connected can be made automatically (eg, via an RFID tag positioned on the neutral electrode). Several other methods of determining the neutral electrode type are possible. It is also possible to enter the neutral electrode type manually before the procedure, or to determine the relevant parameters at a predetermined test location.

  The electrosurgical device can comprise an interruption device that interrupts or limits the high frequency current when a predetermined impedance change is exceeded or when a predetermined temperature is exceeded at the neutral electrode. Configured as follows. It is also conceivable that the interrupting device issues a warning signal when a predetermined impedance value is exceeded.

  The electrosurgical device can include a contact agent layer having material properties such that its impedance decreases with increasing temperature. This means that materials with a negative temperature coefficient can be used. Thus, it is possible to detect a particularly low resistance section resulting from a particularly high temperature over a large area neutral electrode.

In order to determine the temperature and / or temperature change, the temperature measuring device can take into account the high frequency current, in particular the effective value of the applied high frequency current. For example, to determine temperature change and / or resistance, specifically tissue resistance or contact resistance between electrode and tissue, calculate the relationship between impedance change and effective value (eg, ΔR / I _HF ) Is possible. Resistance can provide information regarding how well the neutral electrode is attached to the tissue, among others.

The electrosurgical device may comprise a current integrating device, which sums values associated with the high frequency current, specifically effective values over time, specifically over a predetermined period of time, And this sum is configured to enter into the relationship with the impedance change to determine the temperature and / or temperature change. It is easier and less error prone if both the impedance change and the sum of the applied high frequency current over a predetermined time interval are observed. Individual values can be put into a relational expression (eg, ΔR / ΣI _HF ) to record system characteristic values and to determine temperature and / or temperature changes.

The above-mentioned problem is solved also by the method described in claim 15 .

Specifically, the above problems are solved by a method for determining temperature and / or temperature change in a neutral electrode having a contact agent layer, which method comprises the following steps:
a) determining at least one impedance value of the contact agent layer;
b) calculating a temperature change and / or temperature at the neutral electrode based at least on the impedance value.

  The method according to the invention also uses the dependence of the contact layer impedance on the dominant temperature. Rapid heat exchange occurs due to the proximity between the contact agent layer and the applied portion of the neutral electrode and the proximity between the contact agent layer and the tissue. It can be assumed that the temperature of the tissue present directly below the neutral electrode is approximately the same as the temperature of the neutral electrode and the contact agent layer. Therefore, realistic estimation of temperature equilibrium at the neutral electrode can be performed. Unacceptably severe temperature increases due to the applied high frequency current can be recognized and prevented.

  Step a) can be performed multiple times during multiple activation and deactivation phases to determine multiple impedance values. In this method, the temperature pattern or individual temperature change in the neutral electrode can be better evaluated. A realistic assessment of the dominant temperature can also be performed.

  In step b), the duration of the activation and / or deactivation phase and / or the effective value of the high-frequency current can be taken into account.

  Step b) can include the integration of a plurality of impedance values over time.

  The method can include impedance changes during the activation and / or inactivation phases. For example, it is possible to draw conclusions about the dominant temperature based on the ratio of cooling time to impedance change. If the temperature drop between the neutral electrode and the surroundings is steeper, it can be reliably assumed that the neutral electrode cools more rapidly. Thus, impedance changes over time can represent an important parameter in determining temperature.

Specifically, the temperature change is calculated using the following formula:
ΔT = (R (T) −R (T ₀ )) / (α * R (T ₀ ))
Can include linear estimation. However,
α is the inherent temperature coefficient,
T ₀ is the starting temperature,
R (T ₀ ) is the impedance at the starting temperature T ₀ ,
R (T) is the measured impedance.

  Although there is no linear relationship between the temperature and impedance of the contact agent used (preferably a hydrogel), the change in impedance can be approximated sufficiently accurately by a linear equation in its dependence on temperature. Is possible. Alternatively, it can be approximated using higher order polynomials. The inherent temperature coefficient can be determined in advance at an appropriate test site. It is also conceivable to determine a plurality of temperature coefficients for higher order polynomials.

This method
-Detecting the specific type of neutral electrode connected;
-Depending on the type of neutral electrode, it may include selecting a predetermined temperature coefficient or any other parameter.

  Thus, pre-determined parameters can be automatically included in the method.

  The method may include issuing a warning signal and / or switching off or weakening the high frequency current if the measured impedance change exceeds a predetermined limit value. Thus, if an unacceptable temperature occurs, a warning signal is output to interrupt or limit the high frequency current to prevent damage to the patient.

  The present invention will now be described in further detail with reference to some exemplary embodiments shown by way of illustration.

1 shows a high frequency generator system having a monopolar instrument. The components of a high frequency generator system are shown. The state of resistance and electric current in a neutral electrode is shown. Figure 2 shows an idealized resistance-temperature graph.

  In the following description, the same reference symbols are used for identical parts and parts that act similarly.

FIG. 1 shows an electrosurgical device comprising a radio frequency generator system 30, a monopolar instrument 20, and a neutral electrode 10. The high frequency generator system 30 provides a high frequency current I _HF that is applied to the barrel 1 by the monopolar device 20 and the neutral electrode 10. FIG. 1 shows a schematic cross-sectional view through the body 1. The neutral electrode 10 is affixed to the trunk 1 over a large area. The monopolar device 20 includes an active electrode, which has an area that is substantially smaller than the neutral electrode 10. Current flows from the active electrode to the neutral electrode. In the immediate vicinity of the active electrode, the current density is high, so that the intended coagulation or fragmentation of the tissue 3 (see FIG. 3) can be carried out.

FIG. 2 shows the major components of the high frequency generator system 30. These include a control device 36, a display device 32, an operating device 34 and a measuring device 37. The operator of the electrosurgical device can activate or deactivate the high frequency current I _HF by means of the operating device 34. It is also possible to set different operation modes, for example, one mode for cutting the tissue and another mode for coagulating the tissue. Depending on the information from the user, the control device 36 controls the high frequency generator 31, which provides the high frequency current _IHF according to the input. The display device 32 can be used to display the parameters as they are set, for example to display the current operating mode. The display device 32 can display the current dominant temperature at the neutral electrode 10 and can output a warning message, thereby protecting the patient from unwanted damage from the procedure. According to the present invention, the temperature of the neutral electrode 10 is determined by the measuring device 37 using the secondary current source 38. As soon as the neutral electrode 10 reaches a temperature that can cause a burn, the high frequency generator 31 is switched off and the display device 32 outputs an associated warning message.

  In an exemplary embodiment of the neutral electrode 10 according to the present invention (see FIG. 3), the neutral electrode comprises a first electrode section 11 and a second electrode section 11 '. The electrode sections 11, 11 ′ are arranged on the support material so that these sections are electrically insulated from one another.

In one embodiment of the neutral electrode 10, an electrical insulator or hydrogel 13 is provided between the individual electrode sections 11, 11 '. Included in the present exemplary embodiment is an adhesive neutral electrode 10 comprising a layer of conductive hydrogel 13 and affixed onto tissue 3 for applying a high frequency current _IHF . The present invention takes advantage of the fact that the hydrogel 13 has a high temperature coefficient of impedance. For example, for a commercially available neutral electrode 10 and a commercially available hydrogel 13 with a temperature range of 25 ° C. to 40 ° C., a relative impedance change in the range of 2% to 4% per degree Celsius is measured. This effect can be used to determine the temperature rise at the neutral electrode 10. However, various other parameters must also be considered. For example, environmental conditions greatly affect the impedance measurement value R (T).

In order to measure an impedance R (T) that depends on the temperature T, the measuring device 37 comprises a secondary current source 38. This provides a measured current I _Mess applied to the electrode sections 11, 11 ′. The measured voltage U _Mess can be determined by a voltage measuring device 39 connected in parallel to the secondary current source 38. Therefore, the measuring device 37 can measure the overall impedance. In the first model, this overall impedance is assumed to consist of a plurality of resistors as shown in FIG. Thus, the measured current I _Mess passes from the first electrode section 11 through the hydrogel 13 and at least partially into the tissue 3, again through the hydrogel 13 and then reaches the second electrode section 11 ′. The overall impedance consists of a gel resistance R _Gel1 , a tissue resistance R _Gewebe, and a second gel resistance R _Gel2 .

In the first model, it can be assumed that the tissue resistance change is negligible in the relevant temperature range (from about 20 ° C. to 70 ° C.). The measurement device 37 can determine the gel resistance values R _Gel1 and R _Gel2 by the measurement current I _Mess . The tissue resistance R _Gewebe can be determined by further measurements or can be set to a constant value that matches the approximate resistance generated in the tissue.

In the second model, it is assumed that the gel resistance values R _Gel1 and R _Gel2 are lower than the tissue resistance R _Gewebe , and thus the measurement by the measurement device 37 includes only a change in the impedance R (T) of the hydrogel 13. The hydrogel 13 can thereby be selected.

In the third model, which best models the reality when using a typical hydrogel 13, it is assumed that the resistance of the hydrogel 13 is greater than the resistance of the tissue 3. This can often occur in practice, especially due to the small layer thickness of the hydrogel 13. Experiments have shown that 30% of the current flow occurs inside the hydrogel layer and 70% of the current flow occurs in the tissue. It is also conceivable that only 10% of the current flow occurs in the hydrogel 13. Therefore, as shown in FIG. 3 , the impedance R (T) is composed of gel resistance values R _Gel1 and R _Gel2 and a tissue resistance R _Gewebe . In the case of this model, the tissue temperature at the time of applying the high frequency current I _HF changes only relatively slowly compared to the temperature of the hydrogel 13 (the blood circulation leads to a rapid deprivation of the generated thermal energy). Again, a constant or nearly constant value for R _Gewebe can be assumed. The effect of the temperature of the tissue 3 on the impedance change ΔR in the tissue is only slight. Therefore, according to the present invention, ΔR can be detected.

Since the gel resistance values R _Gel1 and R _Gel2 rapidly decrease as the temperature T increases, a further advantageous effect is generated. Assuming point heating or local heating of the neutral electrode 10, it is possible to detect a rapid drop in the measured impedance R (T) in this region.

The thermal effects that occur in both the tissue 3 and the hydrogel 13 and the neutral electrode 10 can be attributed to the applied high frequency current _IHF . When the two electrode sections 11, 11 ′ are used, the high-frequency current I _HF is divided into two high-frequency partial currents I _HF1 and I _HF2 . These high-frequency partial currents I _HF1 and I _HF2 are schematically shown in FIG.

  In this exemplary embodiment, it is assumed that the relationship between the impedance R (T) of the hydrogel 13 and its temperature T can be modeled sufficiently accurately by the first order temperature coefficient α. Alternatively, higher order temperature coefficients can be included in this.

From a mathematical viewpoint, the temperature change ΔT can be obtained as follows.
ΔT = (R (T) −R (T ₀ )) / (α * R (T ₀ ))
Here, R (T) is an impedance measurement value at temperature T, R (T ₀ ) is an impedance at start temperature T ₀ , and α is a specific temperature coefficient. The intrinsic temperature coefficient α can be determined, for example, within a test setup.

  The function of the measuring device 37 can be described with reference to the graph in FIG.

The X axis represents the passage of time t in seconds. The Y axis represents the measured values R ₁ , R ₂ , R ₃ , R ₄ of the impedance R (T) in ohms (lower line) and the dominant temperature T (t) at the neutral electrode 10 in degrees Celsius. Expressed in units (upper line). In the Y direction, the temperature values T ₁ , T ₂ , T ₃ , T ₄ decrease, and the impedance values R ₁ , R ₂ , R ₃ , R ₄ increase in the Y direction.

This graph shows, as an example, the course of a high frequency treatment using the neutral electrode 10 according to the present invention. Immediately after application of the neutral electrode 10, the first temperature value T ₁ is established in the hydrogel 13. The first temperature value T ₁ substantially corresponds to a body surface temperature of about 32 ° C. The measuring device 37 can detect the _first impedance value R1. At time t _1, the high-frequency generator 31 is activated at a lower power level (shown schematically by a lamp in the graph). Activation step continues until time _{t 2.} During the activation step, the measured value of the impedance R (T) falls to the impedance value R _3. Since the starting temperature T ₁ , the starting impedance R ₁ and the impedance value R ₂ at the time t ₂ are known to the measuring device 37, the measuring device can calculate the temperature change ΔT using the above-described equation. Absolute temperature value T ₃ may be determined with this basis.

During the inactivation phase (from time t ₂ to t ₃ ), the measured value of impedance R (T) increases. Again, since R ₂ is measurable and R ₃ and T ₃ are known, the temperature change ΔT can be determined on the basis of this impedance change ΔR. Accordingly, the measuring device 37 can calculate the temperature T ₂ from the current temperature change [Delta] T. In the activation phase of the high frequency generator 31 which follow (from the time t ₃ to t _4), the temperature T of the neutral electrode (t) rises again. Again, the temperature change ΔT can be calculated.

  An exemplary embodiment for determining the temperature T (t) and the temperature change ΔT according to the invention in the neutral electrode 10 has already been described.

  In other exemplary embodiments, use of other parameters is possible. For example, it is conceivable to consider a temperature change ΔT in a certain time interval. Therefore, a sudden temperature drop during a relatively short deactivation phase will cause a sudden temperature drop towards the environment, so that a relatively high temperature T (t) exists in the neutral electrode 10. Can be used as a guideline. There are several other methods that utilize the effect that a direct correlation exists between the impedance change ΔR of the hydrogel 13 and its temperature change ΔT.

1: Torso 3: Tissue 10: Neutral electrode 11, 11 ': Electrode section 13: Hydrogel 20: Monopolar instrument 30: High frequency generator system 31: High frequency generator 32: Display device 34: Operating device 36: Control device 37: Measurement device 38: Secondary current source 39: Voltage measurement device ΔR: Impedance change ΔT: Temperature change T (t): Neutral electrode temperature R (T): Impedance I _Mess : Measurement current U _Mess : Measurement voltage R _Gel1 , R _Gel2: gel resistance R _Gewebe: tissue resistance I _HF: high frequency current _{I HF1,} I _HF2: high frequency part current _{t 1, t 2, t 3} , t 4, t 5: the time _{T 1, T 2, T 3} , T _4: temperature values _{R 1, R 2, R 3} , R 4: the impedance value T: temperature α: temperature coefficient

Claims (11)

An electrosurgical device,
A high-frequency generator (31) for generating a high-frequency current (I _HF ) that can be guided into the living tissue (3) via the instrument (20) and the neutral electrode (10) having the contact agent layer (13). )When,
A temperature measuring device (37) for determining at least one of temperature and temperature change (ΔT) in the neutral electrode (10),
The temperature measuring device (37) is configured to detect an impedance (R (T)) of the contact agent layer (13) to determine at least one of the temperature and temperature change (ΔT). With an impedance measurement device
The impedance measurement device comprises a measurement current generator configured to provide a measurement current (I _Mess ) to the first electrode section (11) and the second electrode section (11 ′),
The contact agent layer (13) comprises a hydrogel;
The electrode sections (11, 11 ′) are disposed on the contact agent layer (13) so as to be electrically insulated from each other,
An electrosurgical device , wherein the temperature measuring device (37) considers an effective value of the high frequency current (I _HF ) in order to determine at least one of the temperature and temperature change (ΔT) . The electrosurgical device of claim 1, wherein the measurement current generator is configured to supply a measurement current (I _Mess ) with an alternating voltage. The electrosurgical device according to claim 1 or 2 , characterized in that the high-frequency generator (31) is configured to supply a high-frequency current (I _HF ) with an alternating voltage with a frequency of 300 kHz or more. The electrosurgical device according to any one of claims 1 to 3 , wherein the contact agent layer (13) has an electrical impedance exhibiting temperature dependence. The temperature measuring device (37) comprises an impedance integrating device configured to integrate an impedance change (ΔR) over a predetermined period of time defined for performing thermal equilibrium estimation. The electrosurgical device according to any one of to 4 . 6. Electrosurgical device according to claim 5 , characterized in that the predetermined period comprises a plurality of activation and deactivation stages of the radio frequency generator (31). Parameters of the at least one electrode area of the neutral electrode (10), or characterized in that it comprises a recognition device for determining at least one of the parameters of temperature coefficient (alpha), according to claim 1 to 6 The electrosurgical device according to any one of the above. The recognition device includes a database having a plurality of parameters and a plurality of neutral electrode types, and the recognition device detects a connection of a specific neutral electrode type and reads the parameters from the database as appropriate. The electrosurgical device according to claim 7 , wherein the electrosurgical device is configured as follows. When it exceeds a predetermined impedance change, characterized in that it comprises an interruption device configured to interrupt or limit the high frequency current (I _HF), to any one of claims 1-8 The electrosurgical device described. It said contact adhesive layer (13) is characterized by having material properties such as its impedance decreases with increasing temperature, electrosurgical device according to any one of claims 1-9. In order to determine at least one of the temperature and the temperature change, the effective values of the high-frequency current (I _HF ) are summed over time and the total value is put into a relational expression with the impedance change (ΔR). The electrosurgical device according to claim 1 , comprising a current integrating device configured.

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